1. Field of the Invention
The present invention relates to a plasma display panel (PDP) for display an image.
2. Description of the Related Art
Generally, a PDP is a display device in which vacuum ultraviolet (VUV) rays emitted from the plasma generated by gas discharge excite phosphors to emit red, green, and blue visible light and thereby realize predetermined images. The PDP can provide a large-scale screen of more than 60 inches with a thickness of less than 10 centimeters. Since the PDP is a self emission display device, it typically has no distortion due to view angle and has outstanding color reproduction. Moreover, its manufacturing process is simpler than that of an LCD, so the PDP has advantages in productivity and cost. Accordingly, the PDP has been highlighted for televisions and flat panel displays for industrial purposes.
In a typical AC PDP, address electrodes are formed along one direction on a rear substrate, and a dielectric layer is formed on an entire surface of the rear substrate, covering the address electrodes. Over the dielectric layer, a plurality of barrier ribs are formed in a stripe pattern between each of the address electrodes, and red, green and blue phosphor layers are formed between each of the barrier ribs.
Further, display electrodes having a pair of transparent electrodes and a pair of bus electrodes, are typically formed in a direction intersecting the address electrodes on a surface of a front substrate opposing the rear substrate. A dielectric layer and an MgO protective layer are formed sequentially covering the display electrodes.
Discharge cells are defined in the region where the address electrodes on the rear substrate intersect a pair of the display electrodes on the front substrate.
In the aforementioned PDP, more than a million matrix type discharge cell units are arranged. To simultaneously drive matrix type discharge cells of an AC PDP, a memory characteristic is used which will be described in more detail below.
In order to induce discharge between an X electrode and a Y electrode, forming a pair of display electrodes, a potential difference of not less than a predetermined critical voltage is required. The predetermined critical voltage is referred to a firing voltage Vf. An address voltage Va is applied between the Y electrode and the address electrode, and the discharge occurs forming plasma within discharge cells. This occurs because electrons and ions in the plasma shift toward electrodes with opposite polarities, thereby permitting the flow of electric current.
Dielectric layers are formed on the respective electrodes of the AC PDP. Most of the charge carriers (for example, electrons or ions) are deposited on whichever of the dielectric layers has polarity opposite that of the charge carrier. The net potential between the Y electrode and the address electrode is smaller than the originally applied address voltage Va, so that the discharge becomes weak, resulting in dissipation of address discharge. In such a case, a relatively small amount of electrons is deposited on the X electrode, while a relatively large amount of ions is deposited on the Y electrode. The charge deposited on the dielectric layer covering the X and Y electrodes is a wall charge Qw. A space voltage formed between the X and the Y electrodes due to the wall charge is a wall voltage Vw.
Subsequently, when a predetermined voltage, that is, a discharge sustain voltage Vs, is applied between the X electrode and the Y electrode of the selected discharge cell, plasma discharge is effected when the sum of the discharge sustain voltage Vs and the wall voltage Vw, that is, (Vs+Vw), exceeds a discharge firing voltage Vf. Accordingly, vacuum ultraviolet rays (VUVs) are emitted from discharge gas excited by plasma discharge. The VUVs excite phosphors so that they emit visible light through the transparent front substrate.
However, if any address discharge is not induced between the Y electrode and the address electrode, that is, if the address voltage Va is not applied thereto, no wall charge is deposited between the X and Y electrodes. As a result, no wall voltage exists between the X and Y electrodes. In such a case, only the discharge sustain voltage Vs applied between the X and Y electrodes is made within the discharge cell. Since the discharge sustain voltage Vs is lower than the firing voltage Vf, the gas space between the X and Y electrodes may not cause the discharge.
The PDP driven in the above-described manner undergoes several operational steps from inputting of power to finally obtaining of visible light. In this regard, on the one hand, in order to initiate sustain discharge, the X and Y electrodes are required to be rather close to each other or a considerably high sustain discharge voltage needs to be applied thereto. On the other hand, in order to increase the luminous efficiency through excitation of phosphor layers formed on discharge cells, a long gap must be maintained throughout the area where sustain discharge takes place.